Control system for concrete placer



Feb. 4, 1969 R. H. MOT-r CONTROL SYSTEM FOR CONCRETE PLACER Filed Jan. 51, 1967 l/YVE/vrak R/cf/ARD /7. N077 By v l a Arr Y United States Patent O 3,425,356 CONTROL SYSTEM FOR CONCRETE PLACER Richard H. Mott, Sioux Falls, S. Dak., assignor to J. I. Case Company, Racine, Wis., a corporation of Wisconsin Filed Jan. 31, 1967, Ser. No. 612,839 U.S. Cl. 103-49 Int. Cl. F041) 17/00, 7 00, 49/00 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a control system for a reciprocating pump and more particularly to a hydraulic iluid control system for a concrete placer.

Control systems for previous pumps of the type which pump slurry or aggregate-containing material have not been entirely satisfactory because it has been diicult to properly time and sequence the operation of the reciprocating devices.

Background of the invention The present invention is an improvement over the control system disclosed in U.S. Patent Nos.: 3,198,123 and 3,205,906, which show a pump and valve assembly having control valves, limit switches, and relays as the major components of the control system. A description of the pump and valve assembly or of the concrete placer, as the unit is noW commonly called, is adequately disclosed in the above-mentioned patents and will not be repeated in detail in this specification. However, the control system covered by the present invention is different from that in the above patents, and the principal object of this invention is to provide an improved control system for a concrete placer.

Another object is to provide a control system which assures a full stroke of the material delivery devices.

A further object is to provide a control system such that there is no backow of material during the pumping operation.

Another object is to provide a control system which compensates for system uid which may be lost through leakage.

An additional object is to provide a control system which purges the system itself of excess oil during the time that the delivery device is operating.

Additional objects and advantages will become apparent from a reading of the following description taken together with the annexed drawing.

As shown on the drawings:

FIGURE l schematically illustrates the concrete pump with the present invention incorporated therein; and

FIGURE 2 shows an enlarged sectional view of the iluid cylinder piston and relief valve.

As stated above, the concrete placer, of which the present invention is a part, will not be described in detail; however, a general summary of operation is believed to be necessary to provide a background for this control system. The concrete placer generally includes a hopper to receive the material, a pair of delivery devices or cylinders, double-acting reciprocating in nature to move ice the material along a restricted path a prime mover for powering the delivery cylinders and associated mechanism, valve means for regulating the ilow of material into the path of the delivery pistons, control valves for controlling operation of the valves `means and the delivery cylinders, and a control system for properly coordinating the operation of the control valves in relation to the reciprocating cycle.

As seen in the single diagrammatic view, the concrete placer includes a pair of placement cylinders 20 and 22 having positioned therein placement pistons 24 and 26 connected to rods 28 and 30. Adjacent to and in line with cylinders 20 and 22 are hydraulic or power cylinders 32 and 34. A hopper, not shown, receives the material to be pumped or placed and this material is moved from the placement cylinders 20 and 22 to the left, as seen in the drawing, by the placement pistons. Thus, the pistons 24 and 26 both discharge the material, which material is drawn through lines from the hopper, and then pumped into a common manifold and thence through a delivery line. The pistons 24 and 26 are reciprocated within the cylinders 20 and 22, respectively, in such a manner that, as one piston moves to the right, the other moves in the opposite direction. As a piston moves to the right, concrete or other slurry-type material is drawn from the hopper through either of the ports 36 and 38 into the respective placement cylinder. As a piston moves to the left, it pumps or discharges the material which has been drawn from the hopper on a previous back stroke. The material is then discharged out a port 40 or 42 into a common manifold, not shown.

As shown in the drawing, rod 28 extends through a partition 44 connecting placement and power cylinders 20 and 32 and rod 30 extends through a partition 46 connecting cylinders 22 and 34. Rod 28 is connected to a hydraulic or power piston 48 and rod 30 is connected to a power piston 50. Cylinder 32 includes an end cap S2 and cylinder 34 has an end cap 54, which caps will be more fully described as a part of the invention.

A hydraulic pump 56, driven by a prime mover, not shown, delivers a quantity of pressurized uid into the system for powering of the pistons and for control purposes. Separate pumps may be used for these functions, as required by the particular system. A placement control valve 58 is connected by hydraulic lines 60 and 62 to the upstream or piston end of power cylinders 32 and 34 respectively. A line 61 connects pump 56 and valve 58. A common line 64 connects the downstream or rod ends of cylinders 32 and 34, and a line 63 connects the pump 56 to line 64.

Downstream of placement cylinders 20 and 22 are inlet and outlet valves which alternately open and close to control the ow of material out through ports 40 and 42. The inlet valves 66 and 68 include cylinders 70 and 72 having rods 74 and 76 and pistons 78 and 80 actuated by hydraulic fluid which is controlled by a valve control valve 82. Similarly, the outlet or delivery valves 84 and 86 include cylinders 88 and 90 having rods 92 and 94 and pistons 96 and 98 actuated by the hydraulic uid and controlled by valve 82.

Valve 58 is a solenoid-controlled four-way valve and valve 82 is a solenoid-controlled, dual-stack, four-way valve. These valves are conventional type in that they have been utilized in the prior art, as shown in the abovementioned patents, and it is not necessary to further describe them in detail.

Control valve 82 is connected to the inlet and outlet valves by means of hydraulic lines as follows: Line 100 connects the downstream face of piston 78 to one side of valve 82, and to the -downstream face of piston 98; line 102 connects the upstream face of piston 78 to the upstream face of piston 98 and to one side of valve 82; line 104 connects the downstream face of piston 80 to one side of valve 82 and to the downstream face of piston 96; and line 106 connects the upstream face of piston 80 to the upstream face of piston 96 and to one side of valve 82.

It is thus seen that the inlet valve of one materialcarrying line is hydraulically connected to the control valve 82 and to the outlet valve of the other material line, so that the-inlet and outlet valves work together in the control of admitting material and pumping the material out the ports and 42.

A pressure switch 108 is connected by a uid line 110 to the upstream face of piston 96 and a pressure switch 112 is connected by a fluid line 114 to the upstream face of piston 98. As the system pressure builds up in either of cylinders 88 or 90, the respective pressure switch is closed which actuates the valve solenoids.

A limit switch 116 is positioned in the control system such that it is actuated from either of the hydraulic pistons 48 or 50. A limit switch actuator pin 118 extends through partition 44 in a position such that the pin is contacted by piston 48 in one direction of piston travel. A limit switch actuator arm 120 is pivotally connected at pin 122 and is attached to actuator pin 118 so that when piston 48 moves to the left, in the drawing, the arm is swung into position to close switch 116. Similarly, a limit switch actuator pin 124 extends through partition 46 to be contacted by piston 50. An actuator arm 126 is pivotally connected at pin 128 and attached to pin 124 so that when piston 50 moves to the left in cylinder 34, the arm is swung to close the limit switch.

As stated, hydraulic cylinder 32 has an end cap 52 which also provides a support for a valve actuator stud 128. Likewise, cylinder 34 has an end cap 54 and a stud 130. Piston 48 includes a relief valve 132 and piston 50 has a relief valve 134. These relief valves are a part of the hydraulic 4slave system on the placement or delivery cylinders to assure that the cylinders maintain a full length stroke in the pumping cycle. The valve actuator studs 128 and 130 extend through the end caps of the respective cylinders. As piston 50 moves to the right due to the force of the fluid on the downstream face of the piston, stud 130 contacts the valve 134 and relieves the pressure by allowing excess oil out through line 62. This is accomplished by reason of the fluid on the downstream face of piston 50 urging relief valve 134 in its seat to seal the upstream face of the piston during this part of the cycle. As the piston nears the end of its travel, stud 130 contacts valve stem 134a and displaces it so that a certain amount of fluid flows through the valve 134 and into line 62. Similar operation is realized by the valve piston 48 during its cyclic movement. Line 64 connecting the downstream sides of cylinders 32 and 34 is utilized to carry the fluid from a constant volume valve 136 in line 63.

The solenoids on valves 58 and 82 and the electrical controls are interconnected by conventional wiring which is shown in the dotted lines of FIGURE 1. Briefly, the electrical circuit wiring includes a conventional battery 200 having its negative contact grounded with the positive contact connected through line 202 to the base of the two position switch 116. The switch arm 116:1 is adapted to engage either contact for completing respective circuits to the solenoids on the respective valves.

Thus, the first contact 116b is connected through line 204 to the solenoid 58a forming a part of the valve 58. The same contact of switch 116 is likewise connected through line 206 to both solenoids 82a and 82b of the dual-stack, four-way valve 82. The solenoid 82a has its second contact grounded through line 208 while the solenoid 82b has its second contact connected through line 210 to contact 108a of the normally open pressure switch 108. The same contact of the pressure switch 108 4 is also connected to the second contact of solenoid 58a through line 212.

The contact 116e of switch 116 is similarly connected to the remaining solenoids on the two valves. Thus, line 220 connects contact 116C directly to a first contact on solenoid 58b of valve 58 while branch line 222 connects contact 116C to the first contact of the respective solenoids 82C and 82d. The second contact of solenoid 82e` is again grounded through line 208 while the second contact of solenoid 82d is connected through line 224 to contact 112a of pressure switch 112. Contact 112a of pressure switch 112 is likewise connected through line 226 to the second contact of solenoid 58h while the normally open pressure switch is grounded through yline 228.

In the operation of the improved hydraulic control, one of the hydraulic pistons, i.e., piston 48 is extended to the left in the drawing, and oil is forced from the downstream side of the piston through the slave line 64 to the downstream face of piston 50 causing it to retract or move to the right in the drawing. At the same time, oil from the pump 56 is forced through the constant volume valve 136 and into line 64 which adds to the amount of oil owing from cylinder 32. This increased amount of oil causes piston 50 to retract at a slightly faster rate than piston 48 is being extended. When the retracting cylinder reaches nearly the end of its stroke, the valve actuator stud 130 contacts the relief valve 134 and moves it oi its seat, in this instance the relief valve including a ball is movable within the piston. As the extending cylinder piston 48 continues to the end of its stroke, the excess oil from the slave line 64 passes through the opened relief valve 134 to a return line, and therefore allows travel of the extending cylinder piston until the full length stroke is reached. At this time, the limit switch actuator pin 118 is engaged by the piston 48, the actuator arm is swung into position and the limit switch 116 is closed to actuate the electrical circuits. This control system automatically compensates for oil lost through leakage and purges the system of excess oil on each stroke of the power piston so that the piston can move along its full length before starting the next cycle.

During the placement stroke of pistons 24 and 48, inlet valve 36 is closed and outlet valve 84 is open. The material to be pumped passes from the hopper into the placement line but, of course, cannot ow back into the hopper. As the retracting pistons 26 and 50 move upstream, inlet valve 38 is open so that material ows from the hopper into cylinder 22 and outlet valve 86 is closed to prevent material from returning through port 42 back into the placement cylinder.

.When the limit switch 116 is closed by reason of the piston 48 moving the pin 118 and arm 120, at the end of the placement stroke switch arm 116a engages contact 116b and the electrical circuit is closed thereby supplylng power from battery 200 to line 204 and branch line 206 to actuate the solenoid 82a. The open valves are then closed by the hydraulic fluid flow through the lines. At this particular time, all four of the inlet and outlet valves are closed and the power of battery 200 is supplied to the solenoid 58a through line 204 and solenoid 82b through line 206 but the valves are not actuated at this time because the solenoids are presently not grounded. As the hydraulic pressure builds up, the pressure switch 108 is closed, energizing the electrical circuits through the other solenoid 82b on valve 82 and solenoid 58a on valve 58 by grounding lines 210 and 212 connected to the respective solenoids on valve 82 and the solenoids on valve 58. This operation then opens the opposite inlet and outlet valves and pressurizes the opposite placement piston thereby starting the next placement stroke. By this controlled operation of the inlet and outlet valves, there is never a time when all these valves are open. This is provided so that there is no backilow of material through ports 40 and 42.

The next reversal of the cycle occurs when the piston 50 reaches the eXtreme extended position actuating arm 126 to move switch arm 116g into engagement with contact 116e` of the switch 116 thereby supplying power to solenoid 5811 and solenoids 82e and 82d through lines 220 and 222 respectively. This will of course immediately energize solenoid 82C since the second contact of this solenoid is connected directly to ground thereby closing the two open valves.

After the open valves have closed, the increase pressure will be sensed through line 114 thereby closing the pressure switch 112 and grounding contact 112a through line 224 to thereby complete the circuit to solenoids 58h and 82d. This of course will again reverse the direction of travel of the respective pistons `50 and 48.

It is thus seen that herein shown and described is a hydraulic control which will accomplish the objects as set forth. Variations of this control may occur to those skilled in the art, and it is to be understood that the invention is not limited by the specific embodiment described and shown, or in fact in any manner except as defined in the following claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A hydraulic control system for a double-acting reciprocating pump having a pair of power cylinders, flirst and second supply and delivery lines with iirst and second inlet valve means in respective supply lines and first and second outlet valve means in respective delivery lines, said power cylinders each having a piston reciprocating therein and each operatively connected to a supply line and a delivery line comprising; pressured iiuid supply means including a lirst valve selectively actuatable to supply cuid to extend one of said cylinders and retract the other of said cylinders and a second valve operatively connected to each said valve means for opening the first inlet valve means and closing the second outlet valve means while closing the other of said inlet valve means and opening the other of said outlet valve means, the improvement comprising means for controlling said 4iirst and second valves and including irst switch means actuatable by each of said power cylinders when said cylinders reach an eXtreme position, solenoid means on said second valve responsive to the actuation of said first switch means for closing the open inlet and outlet valve means, pressure responsive means for sensing the closing of said open valves, and second solenoid means on said first and second valves responsive to said pressure responsive means for opening the other of said inlet and outlet valves and reversing the direction of said power cylinders.

2. A hydraulic control system as defined in claim 1, including a conduit interconnecting said cylinders whereby extension of one piston will force uid from the associated cylinder through said conduit to cause retraction of the other of said pistons, the further improvement of means supplying fluid to said conduit to cause a retraction of the other of said pistons at a rate greater than the extension of said one piston.

3. A hydraulic control system as defined in claim 2, including the further improvement of means on each piston for intermittently placing opposite ends of each cylinder in communication whereby the Huid supplied to said conduit is returned to the supply.

References Cited A STATES PATENTS 

